The present disclosure relates generally to the field of semiconductor materials and their fabrication. More specifically, the present disclosure relates to magnetic sensor semiconductor devices and methods of operation and fabrication thereof that use as the detection mechanism the response of a topological-insulator and an insulating coupler to a magnetic field having a particular magnitude and direction.
Magnetic sensors have a large range of potential applications, including, for example, biomedical detectors and non-volatile magnetic memory systems. Magnetic sensors operate based on an active sensing component sensing the presence or absence of magnetic fields having a particular magnitude and direction. The active sensing component senses based on quantum characteristics of the sensing component, such as the Hall Effect, giant or tunnel magnetoresistance, or superconducting quantum interference. Such sensing components often require special operating environments, including, for example, low temperature or a large bias. Additionally, magnetic sensors that utilize such sensing components can require complex fabrication processes that limit scalability.
It has been proposed to use topological insulator material as the active sensing component of magnetic sensors. Topological insulator materials, such as mercury telluride (HgTe), bismuth selenide (Bi2Se3), or bismuth telluride (Bi2Te3), exhibit quantum states of matter having time reversal symmetry, non-trivial topological order and a large band gap that makes them suitable for room temperature applications. A material that exhibits topological insulator characteristics behaves as an insulator in its interior but has conducting states at its surface, which means that electrons can only move along the surface of the material. More specifically, topological insulators possess an insulating bulk/interior, wherein an energy gap separates the highest occupied electronic valence energy band from the lowest empty conduction energy band. Topological-insulators also exhibit gapless surface states that are due to a strong spin-orbit coupling of electrons. Time reversal symmetry protects these conducting surface states from scattering by impurities. In the presence of a sufficiently strong applied perpendicular magnetic field, time-reversal symmetry is broken and an energy gap emerges for these surface states, which results in a change in the resistance of the topological insulator material in response to the magnetic field. Additionally, topological insulators demonstrate a non-saturating linear response to large magnetic fields due to weak anti-localization arising from strong spin-orbit coupling. Also, the temperature range in which a topological insulator material can effectively and reliably respond to an applied magnetic field can be relatively broad (i.e., ranging from absolute zero to 250 degrees Celsius).
Although topological insulators provide technical benefits when used as the active sensing component of a magnetic sensor, there remain areas such as sensitivity, overall performance and scalability in which the performance of topological insulators in magnetic sensing applications can be improved. For example, the magnetic field that is required to break time reversal symmetry of a topological insulator material can be relatively large, typically in the range of approximately 20 Tesla.